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    台灣植物誌 第二版  Flora of Taiwan, 2nd edition    Vol. 3

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    台灣植物誌第二版  Flora of Taiwan, 2nd edition  3: 968

     101A. TRAPACEAE L. 菱科
    HSIEH, CHANG-FU

    Aquatic floating herbs. Emerged leaves rosulate, rhombic to ovate-rhombic, coarsely dentate towards apex, the petioles inflated above the middle; submerged leaves opposite, pinnatisect. Flowers bisexual, axillary, solitary, pedicelled; calyx-tube short, adnate to the lower part of ovary, the limb 4-lobed, the segments often persistent and turning into horns after anthesis; petals 4, free; stamens 4, anther oblong, 2-locular, dehiscing logitudinally; ovary half-inferior, with a conical apex, 2-celled; ovule 1 in each cell. Fruit bony, indehiscent, 1-seeded, with 2-4 horns; cotyledons very unequal.
    One genus about 30 species in tropical and temperate regions of the Old World. Two species and one variety in Taiwan.

    1. TRAPA L. 菱屬

    Characters as the family.

    KEY TO SPECIES AND VARIETIES
    1. Fruit with 4 horns… 2. T. natans var. japonica
    1. Fruit with 2 horns.
    2. Horns straight… 1. T. bispinosa var. iinumai
    2. Horns decurved… 3. T. taiwanensis

    1. Trapa bispinosa Roxb. var. iinumai Nakano in Engl., Bot. Jahrb. 50: 455. 1913. 菱 Photo 79
    Trapa japonica Flerov in Bull. Jard. Bot. Repub. Russe 24: 39. 1925.
    Trapa natans L. var. bispinosa Makino in Bot. Mag. Tokyo 11: 283. 1897; Sasaki, List Pl. Form. 313. 1928.
    An annual. Stems slender with filiform, pinnately divided roots at each node. Leaves ovate-rhombic, 3-4 cm long, 3-5 cm wide, acute at apex, subtruncate to broadly cuneate at base, irregularly toothed towards apex, glabrous above, pubescent beneath; petioles 8-14 cm long, pubescent. Flowers white to pale rose. Fruit 3-4 cm long inclusive of the horns; horns 2, straight.
    Japan, Korea and northeastern China. Taiwan, confined to the northern part.
    TAIPEI: Musha, Chuang 3084; Taipei City, Tanaka & Shimada 11184.

    2. Trapa natans L. var. japonica Nakai in Journ. Jap. Bot. 18: 429. 1942. 鬼菱
    Trapa natans L. var. quadrispinosa Makino in Iinuma, Somoku Dzusetu I, 139. 1901.
    Trapa natans L. var. bispinosa Makino f. quadrispinosa Makino in Bot. Mag. Tokyo 22: 172. 1908, excl. basionym.
    An annual. Leaves broadly rhombic, 3-4 cm long, acute at apex, broadly cuneate at base, irregularly toothed towards apex, entire towards base, glabrous above, densely pubescent beneath; petioles 5-10 cm long, pubescent to nearly glabrous. Flowers white. Fruit more or less tetrahedral, 3-3.5 cm long, the horns 4, sharp.